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 Table of Contents  
ORIGINAL ARTICLE
Year : 2021  |  Volume : 114  |  Issue : 1  |  Page : 21-29

Evaluation of deep anterior lamellar keratoplasty for anterior corneal stromal pathology


Department of Ophthalmology, Ophthalmic Center, Faculty of Medicine, Mansoura University, Mansoura, Egypt

Date of Submission18-Aug-2020
Date of Decision26-Aug-2020
Date of Acceptance01-Dec-2020
Date of Web Publication31-Mar-2021

Correspondence Address:
MS Aya M Hashish
Department of Ophthalmology, Ophthalmic Center, Faculty of Medicine, Mansoura University, Ophthalmic Centre, Al-Gomhoria Street, 35516, Mansoura
Egypt
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/ejos.ejos_50_20

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  Abstract 

Settings This study was conducted in Mansoura Ophthalmic Center, Mansoura University, Egypt, during the period from January 2018 to January 2019.
Purpose This study aimed to evaluate the visual outcomes, topographic features, endothelial cell densities (ECD), and complications of deep anterior lamellar keratoplasty using big-bubble technique (BB-DALK) in different corneal stromal pathologies.
Patients and methods This was a prospective, interventional study that included 24 eyes of 24 patients having corneal stromal pathologies, not involving Descemet membrane (DM) and endothelium. The primary outcome measures were the clinical, visual, and topographic outcomes (uncorrected visual acuity, best-corrected visual acuity, K1, and K2) throughout the follow-up period, whereas the secondary outcome measures were the refractive outcomes, central corneal thickness, ECD, and intraoperative and postoperative complications.
Results A total of 21 (87.5%) patients underwent uneventful BB-DALK, and three (12.5%) cases were complicated by intraoperative DM microperforation who developed DM detachment and double anterior chamber (AC) postoperatively. One of them resolved spontaneously and the other two cases required intracameral air injection. Uncorrected visual acuity improved from 1.55±0.26 (logarithm of minimum angle of resolution) preoperatively to 0.63±0.2 1 year postoperatively (P<0.001) and best-corrected visual acuity improved from 1.08±0.11 (logarithm of minimum angle of resolution) to 0.30±0.12 (P=0.017). Refractive cylinder improved from −7.79±1.75 to −2.85±2.01 at 12 months of follow-up (P=0.007). Average K reading changed from 60.00±7.77 preoperatively to 43.43±2.98 postoperatively (P<0.001). Total ECD was 2248.08±431.13 by the end of the first year, with a mean of 8.2% endothelial cell loss. Loosening of the sutures occurred in five (20.8%) eyes between third and sixth months postoperatively. Urrets-Zavalia syndrome occurred in one of the two cases who were complicated with postoperative double AC and required intracameral air injection.
Conclusions BB-DALK is an effective and safe technique for treatment of different corneal stromal pathologies sparing endothelium and DM.

Keywords: big bubble, deep anterior lamellar keratoplasty, stromal pathology


How to cite this article:
Hashish AM, Awad EA, Sabry D, El-Awady HE, El-Metwally MN. Evaluation of deep anterior lamellar keratoplasty for anterior corneal stromal pathology. J Egypt Ophthalmol Soc 2021;114:21-9

How to cite this URL:
Hashish AM, Awad EA, Sabry D, El-Awady HE, El-Metwally MN. Evaluation of deep anterior lamellar keratoplasty for anterior corneal stromal pathology. J Egypt Ophthalmol Soc [serial online] 2021 [cited 2021 Jul 30];114:21-9. Available from: http://www.jeos.eg.net/text.asp?2021/114/1/21/313080


  Introduction Top


Deep anterior lamellar keratoplasty (DALK) is a surgical procedure in which a diseased corneal stroma is excised until, or as close as possible, the Descemet membrane (DM) followed by transplantation of the donor corneal button free from DM and endothelium [1].

Several corneal stromal pathologies such as stromal dystrophy, stromal scars, or corneal ectasia (e.g. keratoconus) result in visual impairments; however, the DM is frequently normal in these cases. Hence, it makes sense to remove only the diseased stroma [2]. DALK is considered the gold standard procedure in these cases [3].

Lamellar surgery is difficult and time consuming. The major technical difficulty lies in judging the depth of the corneal dissection to be as close as possible to DM without perforation, and unless this is achieved, visual outcome is likely to be compromised [4]. Even in experienced hands, surgery cannot be completed as planned in about 20% of the cases [5].

Different techniques have been described to separate DM from the stroma, to ensure a smooth and uniform recipient–donor interface [6]. Anwar and Teichmann [7] introduced the ‘big-bubble’ (BB) technique, in which air injection is used to dissect the DM from the posterior stroma. This facilitates a safer exposure of DM, with the advantages of shortening the surgical time, reducing the risk of perforation and exposing a smooth even surface with excellent optical quality [8].

This study was carried out to evaluate the visual outcomes, topographic features, endothelial cell densities (ECD), and complications of BB-DALK in the management of corneal stromal pathologies.


  Patients and methods Top


This was a prospective, interventional study conducted in Mansoura Ophthalmic Center, Mansoura University, Egypt, during the period from January 2018 to January 2019. The study followed the tenets of the Declaration of Helsinki and had an approval from local Ethical Committee (MD/16.11.49). A written consent was obtained from each patient after being informed of the risks, benefits, and alternatives of surgery.

The study included 24 eyes of 24 patients having corneal stromal pathologies, not involving DM and endothelium, such as corneal ectasia (e.g. keratoconus or postrefractive keratectasia), corneal stromal dystrophies (e.g. granular or macular), and stromal scars following keratitis. Eyes with a total scarring, defect in DM causing hydrops, ongoing bacterial infection, gross peripheral anterior synechiae, history of prior ocular surgery or trauma, and pre-existing ocular disease like glaucoma or retinal pathology were excluded from the study. Preoperatively, complete history was taken, then full ophthalmic examination was performed including uncorrected visual acuity and best-corrected visual acuity (UCVA and BCVA) using Landolt’s charts and was converted to the logarithm of minimum angle of resolution (LogMAR) for statistical analysis; slit-lamp examination; intraocular pressure (IOP) measurement using air puff tonometer or Tonopen; and dilated fundoscopy. Corneal topographies were acquired with Pentacam HR (Oculus Inc., Wetzlar, Germany) for detecting the average K readings, thinnest corneal location, and average corneal thickness at 7–8 mm corneal diameter (to determine the depth of trephination). Specular microscopy (Topcon SP-2000, Tokyo, Japan) was used for endothelial cell analysis, and anterior segment optical coherence tomography (AS-OCT) (3D DRI OCT Triton; Topcon, Oakland, New Jersy, USA) was used for proper preoperative evaluation and patient selection by measuring the depth of the corneal stromal opacity or apical scar depth in advanced keratoconus cases, for measuring central and peripheral corneal thicknesses, and for evaluating graft–host interface postoperatively ([Figure 1]).
Figure 1 Use of AS-OCT for preoperative patient selection and postoperative evaluation; (a) slit-lamp photography preoperatively showing central corneal scar, (b) AS-OCT showing corneal scar, which did not involve deep stromal layers and DM, (c) slit-lamp photography 1 month after successful BB-DALK, (d) AS-OCT after surgery. AS-OCT, anterior segment optical coherence tomography; BB-DALK, deep anterior lamellar keratoplasty using big-bubble technique; DM, Descemet membrane.

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All the surgeries were performed under general anesthesia and by the same surgeon (H.E.A.). The surgery began with trephination up to 70–80% of stromal thickness using a suction trephine (Hessburg-Barron vacuum trephine; Katena Products, Denville, New Jersey, USA), considering the thinnest point of the cornea in the area of trephination, which was 7.50 or 7.75 mm ([Figure 2]a). A blunt spatula was introduced in the corneal stroma in a paracentral position at an angle nearly parallel to the cornea and was advanced for 2–4 mm to create a track for air injection. A 27-G bottom port cannula attached to a 5-ml air-filled syringe was inserted in the corneal track, and air was gently injected into the mid-stroma until a BB was formed extending till the border of the trephination ([Figure 2]b). Successful BB was identified by the feathery white band at its circular periphery and the increase of IOP ([Figure 2]c). If the BB was not formed after the first attempt, a few more attempts to create a BB were made from different areas of the recipient cornea. After achieving successful BB, a peripheral vertical paracentesis was done to reduce IOP and to confirm successful BB by a small bubble test [9] ([Figure 2]d). Superficial corneal stroma was removed using a crescent blade ([Figure 2]e), followed by Brave Slash using a 15° knife ([Figure 2]f). A blunt spatula was introduced in the space to make sure that the cleavage plane was complete. The stromal layers were divided in four quadrants and excised completely using blunt-tipped microscissors ([Figure 2]g). Afterward, DM and endothelium of a 0.25-mm oversized donor lenticule were stained with trypan blue to enable identification. Next, the donor DM and endothelium were gently stripped off using a dry sponge or forceps ([Figure 2]h), then the tissue was fixed with the host corneal bed using 10–0 nylon monofilament sutures ([Figure 2]i).
Figure 2 Big-bubble deep anterior lamellar keratoplasty (BB-DALK) surgical procedure; (a) initial 80% trephination, (b) insertion of 27 G cannula in the corneal track, (c) injection of air with ‘big-bubble’ formation identified by the feathery white band, (d) intracameral small bubble test (black arrow), (e) superficial keratectomy using crescent blade, (f) brave slash using 15° knife, (g) dissection of the residual stroma above DM using blunt-tipped microscissors, (h) scraping of DM and endothelium using dry sponge, (i) complete suturing of the donor cornea. BB-DALK, deep anterior lamellar keratoplasty using big-bubble technique; DM, Descemet membrane.

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Postoperatively, patients received topical antibiotic (Moxifloxacin) and steroid (prednisolone acetate) eye drops. The antibiotic was discontinued after complete epithelialization, whereas the steroids were tapered slowly and discontinued by the end of first 6 months. Tear-substitute eye drops were also added to help surface epithelial healing. Patients were examined daily for 1 week, weekly for 1 month, monthly for 3 months, then every 3 months till end of the first year. AS-OCT was done from day 1 postoperatively in all cases to confirm compactness of graft–host interface especially in those with DM microperforation. Starting from 1 month postoperative, the following parameters were evaluated: UCVA and BCVA, slit-lamp examination, refraction, keratometric readings, and ECDs. The sutures were removed any time after 6 months if they were seen to contribute to graft neovascularization or cause a significant amount of foreign body sensation or astigmatism.

Descriptive data were collected and analyzed by Microsoft Excel 2010 for Windows. For statistical analysis, we used SPSS (version 22.0 for Windows; SPSS Inc., Chicago, Illinois, USA). For the analysis of quantitative variables, we used average mean±SD values, whereas categorical variables were analyzed by counts and percentages. For the analysis of quantitative measures, we used the Student t test for normally distributed variables. The level of significance was defined as P value less than 0.05.


  Results Top


This study was conducted on 24 eyes of 24 patients who underwent BB-DALK, including seven (29.2%) males and 17 (70.8%) females, with mean age of 28.08±8.622 years. The indications were keratoconus in 22 (91.7%) eyes, one (4.2%) case of postrefractive keratectasia, and one (4.2%) case of postinfectious keratitis corneal stromal scar. All patients included in this study had completed at least 12-month follow-up postoperatively, with mean follow-up period of 16.1±4.2 months. Type I BB, with plane of cleavage between the Dua’s layer and deep cornel stromal, was achieved in 22 (91.7%) patients, and the remaining two (8.3%) patients had type II BB, with the cleavage plane between DM and the posterior surface of Dua’s layer.

In terms of clinical examination, 21 (87.5%) cases underwent uneventful BB-DALK and three (12.5%) cases were complicated by intraoperative DM microperforation. They developed Descemet membrane detachment (DMD) and double anterior chamber (AC) postoperatively. One case was evident by slit-lamp examination as localized corneal edema, and the other two cases showed diffuse and severe corneal edema, making it impossible to visualize the DMD clinically. In the three cases, AS-OCT was very useful to detect the presence, location, and size of the DMD. The first case resolved spontaneously by the end of the first week, whereas the other two cases required intracameral air injection ([Figure 3]). On third month postoperatively, 14 (58.3%) of 24 cases showed clear graft. This number increased to 17 (70.8%) patients at sixth month, and by ninth month, all patients included in our study showed clear grafts.
Figure 3 Case of DM microperforation; (a): slit-lamp photography postoperatively showing severe and diffuse corneal edema, (b) AS-OCT showing DMD with increase in the corneal thickness, (c) slit-lamp photography after intracameral air injection showing clear graft with dilated fixed pupil (by the end of the first week), (d) AS-OCT showing resolution of DMD with reduction in the corneal thickness. AS-OCT, anterior segment optical coherence tomography; DMD, Descemet membrane detachment; DM, Descemet membrane.

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Regarding the visual outcome, it was found that UCVA improved from 1.55±0.26 preoperatively to 0.63±0.2 LogMAR at 12 months postoperatively (P<0.001), and BCVA also improved from 1.08±0.11 to 0.30±0.12 LogMAR (P=0.017). By the end of the first year, 95.8% of eyes (n=23) achieved postoperative BCVA of 0.5 LogMAR or better and 91.7% (n=22) with BCVA of 0.3 LogMAR or better.

Considering the refractive outcome, in the preoperative period, only seven (29.2%) cases had measurable refraction, with mean spherical and cylindrical error of −7.68±1.57 and −7.79±1.75, respectively. At 12 months postoperatively, all cases became refractable, with statistically significant improvement in both spherical and cylindrical errors, as −0.08±2.99 and −2.85±2.01, respectively (P=0.007). Visual and refractive results are shown in [Table 1].
Table 1 Visual and refractive changes through the follow-up period

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From topographic point of view, preoperative mean K1 and K2 were 56.96±7.45 and 63.12±8.44, respectively, which changed postoperatively to 41.62±3.35 and 45.45±2.75, respectively, at 12 months (P<0.001). The mean central corneal thickness (CCT) was 411.17±49.62 µm before corneal transplantation, and 518.83±55.13 µm at 1-year follow-up using Pentacam, which was nearly similar to the readings using AS-OCT (405.25±36.11 preoperatively and 517.96±54.41 at 12 months postoperatively). ECD preoperatively was not recordable. Postoperatively, the ECD was 2248.08±431.13 cells/mm2 by the end of the first year, with a rate of 8.2% endothelial cell loss. These data are displayed in [Table 2].
Table 2  K readings, central corneal thickness, endothelial cell density, and anterior segment optical coherence tomography computed tomography

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Regarding complications, five (20.8%) cases developed loosened suture with wound dehiscence ([Figure 4]) between third and sixth month, which required resuturing in the operating room. Two (8.3%) cases developed DM folds, which did not interfere with the graft clarity ([Figure 5]). Secondary pupillary block glaucoma occurred in two out of three eyes with double AC who required intracameral air injection. They were managed by giving 200 ml Mannitol 20% solution over 20 min, acetazolamide 250 mg three times daily, and topical antiglaucoma medications for 3 days. One of them was resolved completely, and the other one, in addition to elevated IOP, developed irreversible mydriasis and a tonic pupil (Urrets-Zavalia syndrome). Afterward, the elevated IOP was controlled by topical antiglaucoma medications. At third month, anterior subcapsular cataract was observed and cataract extraction with IOL implantation was done at sixth month postoperatively ([Figure 6]).
Figure 4 Broken suture with wound gapping.

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Figure 5 DM fold not interfering with graft clarity. DM, Descemet membrane.

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Figure 6 Case of Urrets-Zavalia syndrome; (a) anterior segment photography 3 months postoperatively showing dilated fixed pupil, anterior subcapsular cataract, and DM folds, (b) anterior segment photography after cataract extraction and IOL implantation at 6 months postoperatively. DM, Descemet membrane.

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  Discussion Top


Over the past two decades, DALK has re-emerged as a procedure of choice for corneal stromal pathologies with favorable outcomes compared with penetrating keratoplasty [10]. BB-DALK, proposed by Anwar and Teichmann [11], allows to gain fast, safe, and direct DM baring, reducing risk of perforation.

This study included 24 patients who underwent BB-DALK and were followed up for 12 months. The primary outcome measures were the clinical, visual, and topographic outcome (UCVA, BCVA, K1, and K2) throughout the follow-up period, whereas the secondary outcome measures were the refractive outcomes, CCT, ECD, and intraoperative and postoperative complications.

Regarding the visual outcome, in our study and by the end of the first year, UCVA and BCVA improved to 0.63±0.2 and 0.30±0.12 LogMAR, respectively. This matches with Cheng et al. [12], who found improvement in UCVA to 0.76±0.4, and BCVA to 0.39±0.3 LogMAR at 12 months postoperatively. Our results also match with Feizi et al. [13] and Javadi et al. [14], who reported that BCVA improved to 0.25 and 0.26 LogMAR, respectively, at final follow-up examination at 12 months. Other studies showed better visual outcome following BB-DALK, such as Knutsson et al. [15] who found marked improvement to 0.09±0.07 LogMAR at 1 year postoperatively. On the contrary, Smadja et al. [16] reported BCVA of 0.88±0.14 LogMAR at 12 months postoperatively, which is considerably lower than our results.

Hathout and Jarstad [17] found that 90.7% of the eyes in DALK group achieved BCVA equal or better than 0.5 LogMAR. This matches with our results, which revealed that 95.8% (23/24) of the patients achieving BCVA equal or better than 0.5 LogMAR. Moreover, Alzahrani et al. [18] found that 81% of eyes achieved BCVA of 0.3 LogMAR or better, which was slightly lower than ours, which was 91.7% (22/24). Fontana et al. [19] reported that visual acuity stabilizes 6 months after BB-DALK and refraction status stabilizes at 12 months. This was against our results, which found that both visual and refractive outcomes stabilized at 12 months postoperatively, with the most significant improvement noticed at 12 months. This difference can be explained by the delayed removal of the astigmatic sutures in our study, which was done at 12th month postoperatively.

In the term of refractive and topographic outcomes, the current study found improvement in the preoperative cylindrical error from −7.79±1.75 to −2.85±2.01 at the end of the first year. This matches with Knutsson et al. [15], who revealed an improvement in the refractive astigmatism from −5.35±3.42 preoperatively to −2.86±1.75 at 1 year. Yüksel et al. [20] showed a slightly higher results than ours, with mean cylinder error of −4.27±2.10 at 12 months postoperatively. In the current study, the mean K reading changed from 60.00±7.77 preoperatively to 43.43±2.98 at 12 months, which nearly matches with Yüksel et al. [20], who showed K reading improving to 44.11±3.59 at 12 months. Regarding CCT, our study revealed a corneal thickness of 518.83±55.13 µm at 1-year follow-up, which was similar to the results of Baradaran-Rafii et al. [21], which was 525.56±47.87 at 1 year and slightly lower than results of Schaub et al. [22], which was 571.7±54.2 µm at 12 months.

Regarding endothelial cell loss and potential graft failure, in our study, ECD by the end of the first year was 2248.08±431.13 cells/mm2. This was nearly similar to results of Schaub et al. [22], Knutsson et al. [15], and Scorcia et al. [23], which was 2264±350, 2264.88±393.93, and 2286.41±475.98 cells/mm2 at 1 year, respectively.

The rate of the endothelial cell loss varies in different studies. Our rate at 12 months postoperatively was 8.2%, which nearly matches with Hathout and Jarstad [17] and Yüksel et al. [20], both reported it as 8.6% at 12 months. Cheng et al. [12] found a higher rate of 12.9% at 12 months postoperatively. Some studies suggested that the most critical period for cell loss was within first month after DALK with stabilization by sixth months postoperatively, and they attributed this to the reason that the removal of corneal stroma and exposure of DM may lead to endothelial cell loss owing to indirect trauma [15],[19],[24].

This observation did not go with our study, as we found that the cell loss continued after sixth month and stabilized by the end of first year. This can be owing to the three cases with DM perforation and also the resuturing of five cases in our study, which may delay the stabilization of the endothelial cell loss.

DM microperforation is the main intraoperative complication in recent studies of DALK. In our study, three (12.5%) eyes had an accidental DM microperforation. None of them required conversion to Penetrating Keratoplasty (PK), but two of them required postoperative intracameral air injection to manage double AC. This was done with the help of AS-OCT for detection, management, and follow-up of DMD. Yüksel et al. [20] reported a nearly similar rate, which was 15.8% (6/38), but with 7.9% (3/38) conversion to PK, and postoperative double AC in one (2.6%) eye, successfully managed with intracameral air injection. Cheng et al. [12] reported slightly higher rates of 32% (9/28), with 18% (5/28) conversion to PK. Jhanji et al. [25] reported DM perforations and conversion to PK in 23% (8/35). On the contrary, the rate of DM perforation has been reported to be lower by Feizi et al. [13], which was 4% (5/126), 4.5% (1/22) by Alnaimy et al. [26], and 7.5% (18/234) by Kubaloglu et al. [27]. This variability in the rate of intraoperative DM perforation can be attributed to the variability in the indication of the surgery. The rate is usually higher in eyes with advanced keratoconus owing to high steep cornea with apical scarring, which may cause DM perforation.A notable issue after DALK was a higher rate of loosened sutures. In our study, five (20.8%) cases were observed, which matches with the result of Huang et al. [8] and Schaub et al. [22], which was 23.8 and 20%, respectively. This can be attributed to the relatively superficial suture track in DALK, which might be done for fear of DM puncture.

Stromal graft rejection did not occur in our study. This also was observed by Yüksel et al. [20] with none of the cases developed stromal rejection. The risk of immune-mediated stromal graft rejection was reported in other studies and manifested as acute stromal edema and/or stromal neovascularization. Olson et al. [28] reported stromal rejection in five (22.7%) patients and Knutsson et al. [15] in four (13%) cases. They were successfully treated with increasing the frequency of topical corticosteroids.

In our series, one (4.2%) case developed Urrets-Zavalia syndrome. This complication can be attributed to pupillary block glaucoma developed when the AC is over-filled with air as part of DALK procedure especially those with DM microperforation and usually related to the degree and duration of the IOP elevation. It was reported by Maurino et al. [29] in three cases and also by Niknam and Rajabi [30] who reported four cases with iris ischemic and fixed dilated pupil. This complication can be avoided by some precautions during intracameral air injection, the pupil should be fully dilated, and the patient is asked to lie supine for 2–3 days postoperatively. IOP should be aggressively controlled with systemic oral acetazolamide and topical antiglaucoma medications for at least 3 days. The limitations of this study were the small sample size and relatively short period of follow-up, which may have some implications on the statistical analysis. Future studies with larger number of patients and longer follow up duration should be performed.


  Conclusions Top


BB-DALK is an effective and safe technique for treatment of different corneal stromal pathologies sparing endothelium and DM.

Acknowledgements

Financial support: Mansoura University Ophthalmic Center.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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    Figures

  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6]
 
 
    Tables

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